This invention relates to a novel process for preparing 1,5-methylene-3,7-dinitro-1,3,5,7-tetraazacyclooctane, also known as dinitropentamethylenetetramine or briefly as DPT, which is an intermediate for producing HMX.
HMX, 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane, is a very powerful military explosive, but its use has been limited by its high cost and availability. Current methods for manufacturing HMX involve the nitrolysis of hexamine. It is known that HMX can be prepared from DPT, and indeed DPT has been identified as a key intermediate in the formation of HMX from the nitrolysis of hexamine, which is also known as the Bachmann process. (W. J. Chute, D. C. Downing, A. F. McKay, G. S. Myers and G. F. Wright, Can. J. Research, 27B, 218(1949); W. E. Bachmann, W. J. Horton, E. L. Jenner, N. W. MacNaughton and L. B. Scott, J. Am. Chem. Soc., 73, 2769(1951); and W. E. Bachmann and E. L. Jenner, J. Am. Chem, Soc., 73, 2773(1951).
In view of the importance of DPT in the synthesis of HMX, a low cost method for producing this intermediate would provide a significant contribution toward reducing the cost of manufacturing HMX. In the past DPT has been prepared by various methods, viz.
(1) nitrolysis of hexamine using acetic anhydride and 99+% nitric acid in acetic acid solvent; PA1 (2) reaction of hexamine dinitrate and acetic anhydride; PA1 (3) reaction of hexamine dinitrate and 90% H.sub.2 SO.sub.4 and neutralization with ammonia to pH 6.5; PA1 (4) reaction of hexamine, 99+% nitric acid and ammonium nitrate, and neutralization with ammonia to pH 6.5; PA1 (5) reaction of nitramide, formaldehyde and ammonia; and PA1 (6) reaction of nitramide, formaldehyde and methylenediamine sulfate.
The reactants used in all of these methods are costly (e.g. acetic anhydride and hexamine), or are difficult to prepare and handle (e.g. nitramide), so that the synthesis of HMX from DPT is more costly than the current process for manufacturing HMX by nitrolysis of hexamine.
An object of this invention is to provide a more economical process for producing DPT by employing reactants which are less costly than those used in prior art methods.